Question:

\[ \int_0^{\pi/2}\frac{\cos2x}{\sin x+\cos x}\,dx= \]

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Factorize \(\cos2x\) as \((\cos x-\sin x)(\cos x+\sin x)\).
  • \(-1\)
  • \(0\)
  • \(1\)
  • \(\frac{\pi}{2}\)
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The Correct Option is B

Solution and Explanation


Step 1:
Use: \[ \cos2x=\cos^2x-\sin^2x \] \[ \cos2x=(\cos x-\sin x)(\cos x+\sin x) \]

Step 2:
Therefore, \[ \frac{\cos2x}{\sin x+\cos x} = \cos x-\sin x \]

Step 3:
\[ \int_0^{\pi/2}(\cos x-\sin x)\,dx \]

Step 4:
\[ =[\sin x+\cos x]_0^{\pi/2} \] \[ =(1+0)-(0+1)=0 \] \[ \boxed{0} \]
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